PDF《resonator》

Appl Phys A (2011) 102: 99C103 DOI 10.

1007/s00339-010-6022-4 Perfect metamaterial absorber based on a split-ring-cross resonator Yongzhi Cheng ・ Helin Yang ・ Zhengze Cheng ・ Nan Wu Received:

7 April

2010 / Accepted:

18 August

2010 / Published online:

9 September

2010 ? Springer-Verlag

2010 Abstract In this paper, we present a polarization-insensitive metamaterial (MM) absorber which is composed of the di- electric substrate sandwiched with split-ring-cross resonator (SRCR) and continuous metal ?lm. The MM absorber is not limited by the quarter-wavelength thickness and can achieve near-unity absorbance by properly assembling the sand- wiched structure. Microwave experiments demonstrate the maximum absorptivity to be about 99% around 10.91 GHz for incident wave with different polarizations. The surface currents distributions of the resonance structure are dis- cussed to look into the resonance mechanism. Importantly, our absorber is only 0.4 mm thick, and numerical simula- tions con?rm that the MM absorber could achieve very high absorptivity at wide angles of incidence for both transverse electric (TE) wave and transverse magnetic (TM) wave. The sandwiched structure is also suitable for designing of a THz and even higher frequency MM absorber, and simulations demonstrate the absorption of 99% at 1.105 THz. Y. Cheng ( ) ・ H. Yang College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079, P.R. China e-mail: cyz0715@126.com H. Yang e-mail: emyang@mail.ccnu.edu.cn Z. Cheng The School of Electronic and Information Engineering, XianNing University, Xianning 437100, P.R. China e-mail: czz8986my@163.com N. Wu National Key Laboratory of EMC, China Ship Development and Design Center, Wuhan, 430064, P.R. China e-mail: nanlife1979@yahoo.com.cn

1 Introduction Since the hypothesis of simultaneously negative permittivity (ε) and permeability (μ) of media was proposed by Vese- lago [1] and ?rst microwave experiments were demonstrated by Smith et al. [2], a new class of arti?cial materials, so- called metamaterials (MMs) has attracted considerable great interest. The research of negative refractive index (NRI) or double-negative material, which usually is composed of sub- wavelength metallic resonance elements [3, 4], has ushered in a new ?eld of science in recent years. The sub-wavelength unit cell that comprises highly conductive and shaped metals such as gold or copper is periodically arranged in the MMs, and, therefore, treated as homogeneous medium. According to effective medium theory, MMs can be characterized by a complex electric permittivity ? ε(ω) = ε1 + iε2 and magnetic permeability ? μ(ω) = μ1 + iμ2 [5]. MMs have been demon- strated in every technologically relevant spectral range from microwave to optical [6C9]. Generally, more or less power losses could be existence when electromagnetic (EM) waves impinge on MMs. Some applications of MMs are required to minimize losses over the operating frequency range, and the existence of losses could deteriorate the performance of some devices, such as superlenses [10C12]. On the contrary, many applications would be desirable to maximize the meta- material losses, such as the MM absorber. N. Engheta ?rst proposed the theoretic view of using metamaterial achieving perfect absorption for EM waves [13], and microwave experiments were ?rst demonstrated by Landy et al. [14], which has become an important aspect in the research of MMs. Recently, from microwave to visible frequencies ranges, various MM absorbers which consist of two or more layers coupling sandwiched resonance struc- tures have been reported [15C20]. The electric response can be obtained from the excitation of the electric resonators by